“Calcutta spans the edge of the Sunderbans. Skins and whole carcasses are the most commonly seized items, although seizures at this hotspot have reduced during the most recent period (2010-12),” said the study conducted by three non-profit agencies, including the WWF.

The other four “hotspots” are Delhi, Ramnagar in Uttar Pradesh, the central region and the Western Ghats.

The study, titled “Reduced to Skin and Bones Revisited”, is based on seizures of live tigers and body parts between 2000 and 2012 in 13 south Asian nations. These include Bangladesh, Bhutan, Cambodia, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Russia, Thailand and Vietnam.

The study mentions 1,425 seizures in all. India, which has the largest tiger population among the nations, had the most cases at 336. Cambodia reported none.

According to the report, “an average of 110 tigers were killed for trade per year or over two per week” from 2010 to 2012, the last few years of the over decade-long study.

“Since only a fraction of tigers in illegal trade is intercepted by law-enforcement (agencies), the scale of the criminal activity represents a serious threat to the survival of wild tigers, generally considered to number as low as 3,200 (worldwide),” said the report.

Most of the “hotspots” are close to reserves. Calcutta is near the Sunderbans and Ramnagar near the Corbett National Park. The central region covers the Kanha and the Pench parks. The Western Ghats are home to the Sathyamangalam reserve in Tamil Nadu.

The exception is Delhi, which isn’t near a reserve and where seizures have been attributed to security as it is the national capital.

“The report has correctly homed in on the hotbeds but nothing can be done to stop this illegal trade unless the spokes of the trade, spread all over the wilderness, are cut off,” wildlife expert Bittu Sahgal said. He suggested the comparatively lower seizures —and possibly less poaching — in the Sunderbans in recent years could be linked to the tough terrain of the marshy delta.

But seizures in the central region —towns like Jabalpur and Balaghat — and the Western Ghats region “persisted throughout” the past decade, the study said.

“The analysis provides clear evidence that illegal trade in tigers, their parts and products persists as a major conservation concern,” says the report whose co-authors are TRAFFIC, a wildlife trade monitoring network, and the International Union for Conservation of Nature (IUCN).

The study offers India a consolation, though: no live tigers were seized despite a sharp increase elsewhere that the report flagged as “the most significant finding”. Of the 123 such cases since 2000, almost half, or 61, were reported in the past three years (2010-12). Thailand topped the list.